Straddle carriers for trailers substantially of the type shown in U.S. Pat. No. 2,982,430 are commonly employed to carry large loads of produce in bins and for other similar purposes. Such loads of produce including apples, pears, etc. may range from 6 to 27 tons with the produce contained in standard size bins.
The bins are stacked in line and the straddle trailer is backed over them. The driver in the tractor cab controls cable-hydraulic motor means to activate a pair of long opposed lifting arms on the trailer, which arms engage beneath the load and lift it as a unit for transport by the trailer. Such construction and mode of operation is fully described in the above-referenced U.S. patent No. 2,982,430.
Despite wide usage of straddle carriers of this type for a number of years, difficulties continue to be encountered in providing a safe and positive locking system for the load lifting arms to prevent the shifting or dropping of the load in transit. Occasionally, a load will be dropped on the highway creating an obviously serious safety hazard and property loss.
The single objective of this invention is to completely solve the above problem and difficulty of the prior art by the provision of a safe and secure positive locking system for the lift arms of straddle carriers which will render it virtually impossible for the vehicle to drop a load in transit and hence will add greatly to the safety of the carrier.
The invention also provides a fail-safe lift arm locking system in which the multiple pivoted locking pawls cannot be withdrawn from locking engagement with their associated toothed ratchet bars on the lift arms until the load on the lift arms is first relieved by the cable-hydraulic system of the carrier. Therefore, should either the air system or the electric system on the carrier associated with the locking pawls fail, the pawls cannot be disengaged from the cooperating ratchet teeth until the lift arms are elevated slightly to relieve the locking pawls of the load.
Standard automotive air brake actuators (cans) may be employed to operate the pivoted locking pawls. The customary four locking units are synchronized in the invention to operate in perfect unison so that a heavy load cannot be locked in while off-balance. This eliminates excessive stresses on the entire carrier which could otherwise result.
The invention can be installed on most existing carriers in the field in attachment kit form, as well as on newly manufactured straddle carriers.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description.